PROJECT SUMMARY Rodents reared in enriched conditions (EC) during childhood and adolescence have a variety of neurobiological and behavioral differences when compared to rodents reared in standard (SC) or isolated conditions (IC). These neurobiological differences impact numerous behaviors, including the response to drugs of abuse. The neurobiological mechanism for this effect remains unclear. Glutamatergic afferents to the mesocorticolimbic pathway mediate the response to psychostimulants and deficits in glutamate homeostasis are hypothesized to contribute to drug addiction. Differential rearing alters glutamatergic function and therefore our overarching hypothesis is that differential rearing alters glutamate homeostasis. In the proposed experiments, we will examine the effects of differential rearing on astrocyte density and transporters, predominately located on astrocytes, that contribute to glutamate homeostasis. We predict that rearing in an enriched condition, compared to a compared to a standard condition, will augment glutamate homeostasis and increase astrocyte density. Conversely, we predict that rearing in an isolated condition, compared to a standard condition, will impair glutamate homeostasis and decreases astrocyte density. Specific Aim 1 will determine the relationship between differential rearing, amphetamine exposure, and transporter function. We will include female rats due to literature indicating that differential rearing results in plasticity differences between male and female rats and we predict that protective effects of enrichment will be most robust in female rats. Specific Aim 2 will determine the effects of differential rearing, amphetamine exposure, and N-acetylcysteine treatment on astrocyte density within the nucleus accumbens. We will measure astrocyte density using immunohistochemistry and predict that enrichment will provide the greatest protection against amphetamine-induced changes in astrocyte density. Specific Aim 3 will determine if astrocyte density varies as a function of contingent versus non-contingent amphetamine exposure in differentially reared rats. We will administer acute and repeated injections of amphetamine to differentially reared rats and examine GLT-1 and xCT expression using immunoblots and astrocyte density using immunohistochemistry. Completion of these aims will characterize the effects of differential rearing in both male and female rats on glutamate homeostasis, with a specific focus on transporters that predominate on astrocytes. Completion of these aims will strengthen the research environment in the Kansas State University Department of Psychological Sciences and will enable students to participate in all phases of a hypothesis-driven research program.